Patent Document 1 discloses a nano-substance containing a fluorine-containing compound represented, for example, by the general formula:Rf[CH2CH(Si(OR)3)]nRf. Patent Document 1 also discloses a nano-composite obtained by further incorporating a specific silane coupling agent into the nano-substance. Patent Document 1 indicates that the fluorine-containing compound is produced by a method comprising reacting a corresponding olefin monomer in the presence of an organic peroxide having an Rf group (perfluoroalkyl group).
Moreover, Patent Document 2 discloses a method for obtaining polyaniline-containing nano-composite particles by oxidizing aniline in the presence of a fluoroalkyl group-containing oligomer represented by the general formula:R1[CH2CR3(COZ)]nR2.Patent Document 2 indicates that the fluoroalkyl group-containing oligomer is obtained by reacting a fluoroalkanoyl peroxide compound and an acrylic acid, etc.
However, perfluoroalkanoyl peroxides used in these methods are very unstable, and have the risk of decomposition or explosion; therefore, special safety measures are required. Patent Document 3 also indicates that a method using a fluorine-based peroxide is not suitable for mass production. Further, since the fluorine-containing functional groups of the fluorine-containing oligomer become bound only to both ends of the oligomer as groups derived from the perfluoroalkanoyl peroxide, which is a polymerization initiator, there are problems that it is difficult to control the fluorine group content, and that the oil-repellent performance derived from fluorine is less likely to be exhibited.
Furthermore, Patent Document 3 discloses fluorine-containing silica composite particles comprising a mixture of silica nanoparticles, a fluorine-containing surfactant represented by the general formula:QOSO2Rft,and a hydrolysate mixture of a functional alkoxysilane or a dehydration condensate thereof, without using a fluorine-based peroxide. Patent Document 3 indicates that the silica composite particles serve as a material that utilizes the chemical and thermal stability of silica, and the excellent water- and oil-repellency, antifouling properties, and catalytic characteristics of the fluorine compound.
However, the fluorine compound used in Patent Document 3 is a surfactant containing a sulfone group SO2, and is produced by electrolytic fluorination method. In the electrolytic fluorination method, a large amount of anhydrous hydrogen fluoride is used in the reaction, which thus requires sufficient safety measures. Other problems are that this method is not suitable for mass production in terms of the characteristics of the reaction, and that the resulting fluorine compounds are very expensive.